A filter press is a filtering device, and one distinguishes among so-called frame filter presses, chamber filter presses, and membrane filter presses. The same design of the filter press housing is involved, but it is outfitted with different kinds of plates (see, e.g., Horst Gasper “Handbook of industrial solid/liquid filtration”, Hüthig-Verlag Heidelberg 1990, pp. 104-111).
Membrane filter presses with interchangeable membranes are known from this prior art for solid-liquid separation. Such filter presses can be used in various areas of application, such as waste water, chemistry, the food industry, metallurgy, pharmacy, and so on. Chamber filter presses have filtration chambers that are formed by specially shaped plates. Each chamber is provided with a membrane on at least one side. Thus, every second plate can be configured as a membrane plate covered with a membrane on both sides. When unfiltered product flows under pressure into the closed filter press, a filter cake is formed on each filtering means until the two layers of cake coalesce and the chambers are completely filled with solid. This first step of pressurized filtration is followed by a second step, press filtration.
During the press filtration, the elastic membranes are blown upon with a pressure medium, so that they expand and narrow the cake space. The cake embedded there is compressed, further decreasing the residual moisture content in the cavities of the cake. With the use of press filtration, extremely high filtration pressures can be avoided during the pressurized filtration, which leads to a cost savings.
DE 102 21 061 B4 discloses a plate arrangement in which filter plates and membrane plates are disposed alternatingly. The filter plate has a filter cloth on either side, which is secured in a recess of the base body of the filter plate. The membrane plate has a membrane on either side, being secured in a recess on either side of a base body of the membrane plate. A filter chamber is formed in the filter press between the one filter cloth of the filter plate and the membrane of the membrane plate. A pressure chamber is formed between the membrane and the base body of the membrane plate.
An additional filter cloth can be placed on top of the membrane plate on either side as the filter press is being assembled.
The filter cloths each extend as far as the margin of the filter and the membrane plates, where they are pressed against each other and thus held in place when the filter press is closed up. Because the filter cloths end at the margin of the plates, there is a risk of liquid dripping out from this region unless additional sealing elements are provided.
For the cleaning of the filter press, the filter press is opened and the filter cakes removed at the bottom. The individual filter and membrane plates are taken out and cleaned in a cleaning device located outside the filter press. Upon opening of the filter press, the filter cloths have to be removed and cleaned separately.
When filter layers are used in place of filter cloths, the filter layers have to be disposed of and replaced with new filter layers.